Jianhui Yuan

High-temperature thermal stability and axial compressive properties of a coaxial carbon nanotube inside a boron nitride nanotube

The structural performance of double-walled C(5, 5)@BN(10, 10) and C(5, 5)@C(10, 10) nanotubes subject to high temperatures is investigated through molecular dynamics simulations. It is found that the inner tube C(5, 5) in the C(5, 5)@BN(10, 10) exhibits less distortion than that in the C(5, 5)@C(10, 10) at annealing temperatures of 3500 and 4000 K. The C(5, 5)@BN(10, 10) and C(5, 5)@C(10, 10) models with different axial compressive strains are optimized using the universal force field (UFF) method. It is found that the critical buckling strains of the inner tubes in the C(5, 5)@BN(10, 10) and C(5, 5)@C(10, 10) are 12.74% and 9.1%, respectively. The critical buckling strain of the former is larger than that of the latter; although the former exhibits greater deformation and energy loss after buckling than does the latter. These phenomena are also analyzed on the basis of the radial distribution function (RDF) and system energy. The results of this study indicate that the outer tube boron nitride nanotube (BNNT) has a better protective effect on the inner tube than does the outer tube carbon nanotube (CNT) under both high-temperature and lower compressive strain conditions. In these cases, the thermal stability and compressive resistance properties of the C(5, 5)@BN(10, 10) are superior to those of the C(5, 5)@C(10, 10).

Effect of grafted amine groups on in-plane tensile properties and high temperature structural stability of borophene nanoribbons

The effects of grafted amine groups on in-plane tensile properties and structural stability of armchair and zigzag borophene nanoribbons (ABNRs and ZBNRs) are investigated by using molecular dynamics. The results show that the Young’s moduli for the ABNR and ZBNR are 1.093 TPa and 0.978 TPa, respectively. Their ultimate elastic strains are respectively about 15.30% and 22.03%, showing distinct ductile and brittle fractures. When the BNRs are grafted with amine groups (–NH2), the moduli of the ABNR and ZBNR increase to 1.125 TPa and 1.016 Tpa, respectively. The ultimate elastic strain for the ABNR increases to 18.23% but that for the ZBNR gets slightly reduced to 21.12%. The fracture modes still remain unchanged. The structural deformation after being subjected to a high temperature of 1500 K shows that there is little difference between the ABNRs and ZBNRs, but the structural deformation for the grafted BNRs is obviously less than that for the non grafted BNRs. The results indicate that grafting amine groups can increase the Young’s moduli, enhance the elastic strain range, reduce the in-plane elastic anisotropy and strengthen the crack resistance. In particular, the grafting of amine groups can significantly strengthen their capacity to resist deformation at high temperature, reduce the thermal expansion anisotropy and improve the structural stability.

Internal friction characteristic and analysis of in-plane natural frequency of trilayer complexes formed from graphenes and boron nitride nanosheets

The internal friction and in-plane natural frequency of a trilayer complex formed by a monolayer graphene sandwiched in the bilayer of boron nitride nanosheets (BN/G/BN) and graphenes (G/G/G) are studied by using molecular dynamics. The investigation shows that the internal friction coefficients for BN/G/BN (∼0.025) are significantly higher than that of G/G/G (∼0.015). The coefficients for both G/G/G and BN/G/BN increased with external pressure. The speed of increase is divided into quick increase, slow increase and saturation stage. The internal friction coefficients for G/G/G and BN/G/BN follow the simple microscopic theory of Amontons laws only when the external pressure exceeds 170 nN. These findings are expected to help enhance the understanding of the mechanism of nano-tribology and provide an effective micro-control method of internal friction. Subsequent analysis shows that the in-plane natural frequency of mid-layer graphene in BN/G/BN is significantly higher than in G/G/G and both increase as the external pressure increases. Moreover, the natural frequency of mid-layer graphene in trilayer complexes, especially in BN/G/BN, is extremely sensitive to external pressure loads.